Frankfurt, Essen, Karlsruhe all holding up legislature (7)
I believe the answer is:
knesset
'legislature' is the definition.
(Knesset is an example)
'frankfurt essen karlsruhe all holding up' is the wordplay.
'holding' indicates the answer is hidden within the clue.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'tessenk' can be found hidden inside 'frankfurt essen karlsruhe all'.
'tessenk' in reverse letter order is 'KNESSET'.
(Other definitions for knesset that I've seen before include "Israel's parliament" , "Israel parliament" , "Israeli parliament" .)